ThemeCrossfadeSelfTestStep walks Switch -> crossfade-observed ->
mid-crossfade-switch -> crossfade-end -> restore using
TryGetActiveCrossfade, returns Waiting frame-by-frame and Pass after
the restore concludes. The mid-switch phase fires a second Switch
within ~100ms of the first observed crossfade and asserts the lerped
value is neither identity-from nor identity-to, exercising the
ArmCrossfade mid-flight-origin override.
QuickPickerSelfTestStep verifies the three new resource strings, the
built-in theme floor (>=10), and Config.Tabs non-empty.
JonKazama-Hellion
a42cc2a97e